class Gio::SettingsBackend

Overview

The #GSettingsBackend interface defines a generic interface for non-strictly-typed data that is stored in a hierarchy. To implement an alternative storage backend for #GSettings, you need to implement the #GSettingsBackend interface and then make it implement the extension point %G_SETTINGS_BACKEND_EXTENSION_POINT_NAME.

The interface defines methods for reading and writing values, a method for determining if writing of certain values will fail (lockdown) and a change notification mechanism.

The semantics of the interface are very precisely defined and implementations must carefully adhere to the expectations of callers that are documented on each of the interface methods.

Some of the #GSettingsBackend functions accept or return a #GTree. These trees always have strings as keys and #GVariant as values. g_settings_backend_create_tree() is a convenience function to create suitable trees.

The #GSettingsBackend API is exported to allow third-party implementations, but does not carry the same stability guarantees as the public GIO API. For this reason, you have to define the C preprocessor symbol %G_SETTINGS_ENABLE_BACKEND before including gio/gsettingsbackend.h.

Defined in:

lib/gi-crystal/src/auto/gio-2.0/settings_backend.cr

Constructors

Class Method Summary

Instance Method Summary

Instance methods inherited from class GObject::Object

bind_property(source_property : String, target : GObject::Object, target_property : String, flags : GObject::BindingFlags) : GObject::Binding bind_property, bind_property_full(source_property : String, target : GObject::Object, target_property : String, flags : GObject::BindingFlags, transform_to : GObject::Closure, transform_from : GObject::Closure) : GObject::Binding bind_property_full, data(key : String) : Pointer(Void)? data, finalize finalize, freeze_notify : Nil freeze_notify, getv(names : Enumerable(String), values : Enumerable(_)) : Nil getv, notify(property_name : String) : Nil notify, notify_by_pspec(pspec : GObject::ParamSpec) : Nil notify_by_pspec, notify_signal notify_signal, property(property_name : String, value : _) : Nil property, qdata(quark : UInt32) : Pointer(Void)? qdata, ref_count : UInt32 ref_count, run_dispose : Nil run_dispose, set_data(key : String, data : Pointer(Void)?) : Nil set_data, set_property(property_name : String, value : _) : Nil set_property, steal_data(key : String) : Pointer(Void)? steal_data, steal_qdata(quark : UInt32) : Pointer(Void)? steal_qdata, thaw_notify : Nil thaw_notify, to_unsafe : Pointer(Void) to_unsafe, watch_closure(closure : GObject::Closure) : Nil watch_closure

Constructor methods inherited from class GObject::Object

cast(obj : GObject::Object) : self cast, cast?(obj : GObject::Object) : self? cast?, new(pointer : Pointer(Void), transfer : GICrystal::Transfer)
new new, newv(object_type : UInt64, parameters : Enumerable(GObject::Parameter)) : self newv

Class methods inherited from class GObject::Object

compat_control(what : UInt64, data : Pointer(Void)?) : UInt64 compat_control, g_type : UInt64 g_type, interface_find_property(g_iface : GObject::TypeInterface, property_name : String) : GObject::ParamSpec interface_find_property, interface_list_properties(g_iface : GObject::TypeInterface) : Enumerable(GObject::ParamSpec) interface_list_properties

Constructor Detail

def self.new #

Initialize a new SettingsBackend.


Class Method Detail

def self.default : Gio::SettingsBackend #

Returns the default #GSettingsBackend. It is possible to override the default by setting the GSETTINGS_BACKEND environment variable to the name of a settings backend.

The user gets a reference to the backend.


def self.flatten_tree(tree : GLib::Tree, path : String, keys : Enumerable(String)) : Nil #

Calculate the longest common prefix of all keys in a tree and write out an array of the key names relative to that prefix and, optionally, the value to store at each of those keys.

You must free the value returned in @path, @keys and @values using g_free(). You should not attempt to free or unref the contents of @keys or @values.


def self.g_type : UInt64 #

Returns the type id (GType) registered in GLib type system.


Instance Method Detail

def changed(key : String, origin_tag : Pointer(Void)?) : Nil #

Signals that a single key has possibly changed. Backend implementations should call this if a key has possibly changed its value.

@key must be a valid key (ie starting with a slash, not containing '//', and not ending with a slash).

The implementation must call this function during any call to g_settings_backend_write(), before the call returns (except in the case that no keys are actually changed and it cares to detect this fact). It may not rely on the existence of a mainloop for dispatching the signal later.

The implementation may call this function at any other time it likes in response to other events (such as changes occurring outside of the program). These calls may originate from a mainloop or may originate in response to any other action (including from calls to g_settings_backend_write()).

In the case that this call is in response to a call to g_settings_backend_write() then @origin_tag must be set to the same value that was passed to that call.


def changed_tree(tree : GLib::Tree, origin_tag : Pointer(Void)?) : Nil #

This call is a convenience wrapper. It gets the list of changes from @tree, computes the longest common prefix and calls g_settings_backend_changed().


def keys_changed(path : String, items : Enumerable(String), origin_tag : Pointer(Void)?) : Nil #

Signals that a list of keys have possibly changed. Backend implementations should call this if keys have possibly changed their values.

@path must be a valid path (ie starting and ending with a slash and not containing '//'). Each string in @items must form a valid key name when @path is prefixed to it (ie: each item must not start or end with '/' and must not contain '//').

The meaning of this signal is that any of the key names resulting from the contatenation of @path with each item in @items may have changed.

The same rules for when notifications must occur apply as per g_settings_backend_changed(). These two calls can be used interchangeably if exactly one item has changed (although in that case g_settings_backend_changed() is definitely preferred).

For efficiency reasons, the implementation should strive for @path to be as long as possible (ie: the longest common prefix of all of the keys that were changed) but this is not strictly required.


def path_changed(path : String, origin_tag : Pointer(Void)?) : Nil #

Signals that all keys below a given path may have possibly changed. Backend implementations should call this if an entire path of keys have possibly changed their values.

@path must be a valid path (ie starting and ending with a slash and not containing '//').

The meaning of this signal is that any of the key which has a name starting with @path may have changed.

The same rules for when notifications must occur apply as per g_settings_backend_changed(). This call might be an appropriate reasponse to a 'reset' call but implementations are also free to explicitly list the keys that were affected by that call if they can easily do so.

For efficiency reasons, the implementation should strive for @path to be as long as possible (ie: the longest common prefix of all of the keys that were changed) but this is not strictly required. As an example, if this function is called with the path of "/" then every single key in the application will be notified of a possible change.


def path_writable_changed(path : String) : Nil #

Signals that the writability of all keys below a given path may have changed.

Since GSettings performs no locking operations for itself, this call will always be made in response to external events.


def writable_changed(key : String) : Nil #

Signals that the writability of a single key has possibly changed.

Since GSettings performs no locking operations for itself, this call will always be made in response to external events.